It is known that a modern aircraft is equipped with systems (or sensors) for imaging (or imagers) which provide pilots with data from monitoring the environment of the aircraft, named hereinafter “monitoring sensors”. Such a monitoring sensor may relate especially to: a radar which provides an image of obstacles or of environmental conditions existing ahead of the aircraft; an enhanced vision system, EVS, comprising an infrared camera which provides the pilots of the aircraft with an enhanced image of a zone ahead of the aircraft under degraded visual condition; and a rolling camera which offers the pilots an exterior view in front of the aircraft to aid it with piloting on the ground.
It is known that the reliability of the information provided by such a monitoring sensor is directly related to its alignment according to a predetermined position. In particular the image of the EVS enhanced vision system, projected onto a head-up display, HUD, must for example be perfectly superimposed on the real image seen by transparency through this head-up display; the radar must carry out a detection in the axis of the aircraft; and the rolling camera must be perfectly aligned with the axis of the aircraft.
The alignment of a monitoring sensor along a predetermined axis tied to the aircraft is fixed during its installation on the aircraft final assembly line.
However, during the life of the aircraft, an event such as an impact with an external object for example, can lead to a misalignment of the monitoring sensor, either directly, or indirectly via the displacement of a structure or structural part which carries the monitoring sensor.
By misalignment is meant a shift of the line of sight of the monitoring sensor, according to which the latter produces images, with respect to a predetermined direction taken into account as reference.
Hence, it is necessary, or at the very least particularly useful, to be able to detect on an aircraft the misalignment of a monitoring sensor during operation, so as not to be induced into error and to have reliable information.